Silver solder



.' Patented Apr. 24, 1945 SILVER SOLDER George Durst, Attleboro, Mass., assignor to Metals & Controls Corporation, Attleboro, Mass, a corporation of Massachusetts No Drawing. Application October 9, 1943,

7 Serial No. 505,668

9Claims. (01. -173) This invention relates to silver solder, and with regard to certain more specific features to lowtemperature-iiowing silver solder.

Among the several objects of the invention may be noted the provision of a low-cost, easilymanipulated silver solder, or what may be called a silver brazing alloy, of low-temperature-flow- 'ing characteristics; the provisionof a solder of the class described which has a high capillarity and thus a high wetting or spreading characteristic on metal surfaces to which it is applied; and the provision of a solder of this class which has sufficient ductility for cold working. Other objects will be in part obvious and in part pointed out hereinafter. i

The invention accordingly comprises the elements and combinations of elements, the propertions thereof, and features of composition, which will be exemplified in the substances and products hereinafter described, and the .scope of the application of which will be indicated in the following claims. One of the best-known easy-flowing silver sol-- ders is composed of silver, copper, zinc and cadmium, in proportions which are presumably close to being a quarternary eutectic. They have a spreading temperature of about 1175 F. to 1180 F. An example of this old solder is by weight) This is a solid at 1160 F; and-completely liquid at 1175F. The free spreading temperature is 40%, all by weight:

about 1175 F. to 1180 F., depending upon the character of the receiving surface.

The present invention reduces the temperature of spreading while very greatly increasing the spreading effect itself of solders of the above class.

, Following is a table of component proportions of thre examples '(II), (III) and (IV), of my new solder, given in percentage weights:

much lower as compared to the above-mentioned spreading temperature of 1175 F. to 1180 F. A given amount of the new solder will spread about twice as much in area on copper. It solidifies at about 1135 F. Its ductility in cold working is comparable to that of the described old solder. Y

The importance of the additions of tin and lead, as compared to possible additions of other materials which might suggest themselvessuch as gallium, indium, 'antimony, thallium, and bismuth, is that indium and gallium are too expensive while the other metals mentioned cause excessive embrittlement.

The small additions of tin and lead, whilesubstantially reducing temperature of spreading and increasing the spreading activity itself, do not lines for solder it has been suggested that the easy-flowing type of solder have introduced therein small additions of lithium. or sodiumor the like, but alkali metals such as these are expensive, diflicult to handle, and in general are used in silver solders having a higher melting range from those herein contemplated.

Suitable .useful ranges of proportions for the invention are as follows, wherein the combined zinc and cadmium contents should Per cent Silver 40-50 Copper 15-19 Zinc 14-20 Cadmium 18-24 Tin plus lead 0.1-5.0

I have obtained satisfactory results with lead only according to the following two 'ratios by per cent weight;

The additions of both tin and lead are however preferable with regard to wetting characteristics.

In view of the above,-it wilLbe seen that the several objects of the invention are achieved and other advantageous results attained.

not exceed As many changes could be made in the above alloy and solder product, without departing from the scope of the invention, it is intended that 7 all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A low-flow-temperature silver solder comprising approximately by weight, 40-50% of silver; 15-19% of copper; 14-20% of zinc; 18-24% of cadmium; and (Ll-5.0% total of tin and lead.

2. Alow-flow-temperature silver solder comprising approximately by weight 40-50% of silver; 15-19% of copper; 14-20% of zinc; 18-24% ver, 45%; copper, 17.5%; zinc, 16.5%; cadmium, 19.7%; tin, 0.5%; and lead, 0.8%.

5. A low-flow-temperature silver solder having ahigh wetting activity comprising approximately by weight, silver, 46%, copper, 17%; zinc, 16.5%; cadmium, 19.5%; tin, 0.5%; and lead, 0.5%.

6. A low-flow-temperature silver solder having a high wetting activity comprising approximately by weight, silver, 45%; copper, 17%; zinc, 16.5%;

cadmium 20.5%; tin, 0.5%; and lead, 0.5%.

7. A low-flow-temperature silver solder having a high wetting capacity comprising approximately by weight the following proportions; silver, 45-50%; copper, 16%;-zinc, 16%; cadmium,

15-21%; and lead, 3-2%. a

8. A low-flow-temperature silver solder having a. high wetting capacity comprising approximately by weight 50% silver; 16% copper; 16% zinc; 15% cadmium; and lead 3%. 9. A low-fiow-temperature silver solder having a high wetting capacity comprising approximately by weight the following proportions; silver, 45%; copper, 16% zinc, 16% cadmium, 21%; and lead, 2%.

, GEORGE DURST. 

